Embedding data in material

ABSTRACT

A method of transferring information signals representing still images, video audio and/or other data comprises sending, the information signals to a recipient apparatus or “viewer”  10  from a server  2  via a network  12.  Data indicative of whether or not further data is to be embedded in the information signals is also sent either with the signals or separately. The further data is embedded in the information signals at the viewer  10  in dependence upon the indicative data. The further data is perceptible in the information signals as to degrade them.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to embedding data in material.“Material” means one or more of still images, video material, audiomaterial, and data material. Material is represented by informationsignals which most preferably are digital signals.

[0003] 2. Description of the Prior Art

[0004] It is known to embed data in material to identify the ownershipof the material and/or to trace the provenance of the material to detectand protect against copyright infringement. Such embedding of data isknown as watermarking.

[0005] Watermarks may be “robust” in that they are difficult to removefrom the material. Robust watermarks are useful to trace the provenanceof material which is processed in some way either in an attempt toremove the mark or to effect legitimate processing such as video editingor compression for storage and/or transmission.

[0006] In the case of images, whether still or moving, a visiblewatermark is useful to allow e.g. a customer to view the image, e.g.over the Internet, to determine whether they wish to buy it but withoutallowing the customer access to the unmarked image they would buy. Thewatermark degrades the image and the mark should not be removable by thecustomer. Visible watermarks are also used to determine the provenanceof the material into which they are embedded. Watermarks may also beapplied to audio material and to other data.

[0007] It is known to use “Digital Rights Management” software toprotect material against misuse. Many companies provide such software,e.g. SealedMedia, Microsoft, InterTrust Technologies, and others. Suchsoftware, which is designed to be secure against unauthorisedmodification, allows the providers of material to securely distributematerial over computer networks and to control the use of the materialby users.

[0008] U.S. Pat. No. 4,890,319 discloses a subscription televisionsystem for distributing programme material protected by copyright tosubscribers. The system comprises a transmitter including a datainsertion circuit for inserting a control bit in a transmitted signalcomprising other control data and the protected programme material. Areceiver of the system includes a memory for storing a pre-assignedsubscriber identification. Upon receipt and identification of thecontrol bit at the receiver, the receiver inserts the subscriberidentification into the programme material so that any unauthorized copymade of the programme material may by found to include the subscriberidentification. The addition of the user identification is imperceptibleto the user but will show up on any copies of the programme material.The user identification is inserted into a television programme “for buta single frame” and “is barely detectable to the subscriber's eye, suchthat no significant impairment in picture quality results”.

SUMMARY OF THE INVENTION

[0009] According to a first aspect of the present invention, there isprovided a method comprising sending to a recipient apparatusinformation signals and data indicative of whether or not further datais to be embedded in the information signals, and embedding the furtherdata in the information signals at the recipient apparatus in dependenceupon the indicative data, wherein the said further data, when embeddedin the information signals, is perceptible, degrading the informationsignals.

[0010] In accordance with the present invention, it is envisaged thatmaterial may be made available to many potential recipients some of whommay have a good business relationship with the provider and others not.Some may be regarded by the material provider as being more trustworthythan others. For example, the material provider may have long standingcontractual relations with some recipients who have proven to be whollytrustworthy, whilst other recipients may be new to the material providerand in the absence of other information will be regarded, initially, asuntrustworthy.

[0011] Thus, only one version of the material may be produced by thematerial provider for all recipients. The further data is embedded inthe material at the reception apparatus of those recipients deemed torequire the use of further data.

[0012] Embedding further data in material can increase the amount ofdata in the material. In the case of video, the data would be added toevery frame and the increase in data may be large. By sending only theindicative data only a relatively small amount of data is sent to thecustomer in addition to the material. The indicative data may be simplya flag indicating whether or not the further data is to be added inwhich case the increase in data sent is very small, e.g. one bit.

[0013] Data defining the form of the further data to be embedded may besent in addition to the indicative data When such data is sent, it issent once for a whole example of material. In the case of video forexample, it would result in a smaller data overhead than adding furtherdata to every frame of the video. The data defining the form of thefurther data may, for example, simply be data defining a mask whichmasks part of an image, or it may identify the provider or the owner ofthe material represented by the information signals.

[0014] Most preferably, in accordance with an embodiment of theinvention, the information signals are sent in data compressed form tothe recipient apparatus and may be stored in data compressed form beforebeing sent. Embedding further data in compressed signals is difficult,possibly requiring the decompression and recompression of the signals.Adding further data to signals before they are compressed may increasethe amount of data to be compressed. In accordance with this embodimentof the invention, the compressed signals are decompressed at therecipient apparatus and the further data is added to the decompressedsignals for at least some recipients. Thus the same compressedinformation may be supplied to all recipients, avoiding the need toprocess signals differently for different recipients before the signalsare sent to the recipients except for varying the indicative dataaccording to the recipient.

[0015] In preferred embodiments of the invention, the recipientapparatus has a store for storing the information signals. Preferablythe information signals are sent to the recipient apparatus incompressed form as described above and are stored in compressed form.The indicative data determines whether the further data is to beembedded in the information signals at the recipient apparatus. In thepreferred embodiment, the further data is embedded when the informationsignals are retrieved from the store for outputting to the recipients.The indicative data may be changed by the provider without needing toresend the information signals, thus allowing the stored informationsignals to be retrieved by the recipient without the embedded furtherdata but under the control of the provider.

[0016] For example, the provider may offer an image for sale. Theprovider sends the image to a customer with indicative data indicatingthe customer can view the image at no cost only if it is visiblywatermarked. The customer stores the image in the recipient apparatus.The watermarked image is displayed at no cost to the customer butinitially with the visible watermark in accordance with the indicativedata. The customer pays for the image. The provider then sends newindicative data allowing the image to be retrieved from the storewithout the watermark.

[0017] Digital rights management is preferably applied. In addition toallowing the information signals to be securely sent to the recipientapparatus, digital rights are defined which restrict the use of theinformation signals at the recipient apparatus. For example informationsignals may not be copied, printed exported to another apparatus orstored other than in the apparatus regardless of whether or not theindicative data is set to embed the further data and regardless ofwhether or not a customer has paid for the information signals.

[0018] According to a second aspect of the present invention, there isprovided a computer program product arranged to carry out the method ofsaid first aspect when run on a suitable computer system. The programmay be provided by a data providing medium, e.g. a data storage mediumor a transmission medium.

[0019] According to a third aspect of the present invention, there isprovided a system for providing information signals, the systemcomprising one or more servers and one or more clients linked to theserver(s) by a data transmission network, the server(s) being arrangedto:

[0020] a) apply digital rights management to the information signals toprotect the information signals against unauthorised access thereto andto allow access thereto at the client(s) according to the digital rightsdefined by the digital rights management,

[0021] b) provide to the client(s) indicative data indicating whetherfurther data is to be embedded in the information signals at theclient(s), and the client(s) being arranged to:

[0022] c) dependent on the indicative signal, embed the further data inthe information signals before providing the information signals to theuser(s), and

[0023] d) allow access to the information signals according to thedigital rights;

[0024] wherein the further data, when embedded in the informationsignals, is perceptible degrading the information signals.

[0025] According to a fourth aspect of the present invention, there isprovided a computer program product comprising a digital rightsmanagement module together with a module operable to embed further datainto information signals protected by the digital rights managementmodule which further data is perceptible in the information signals anda module operable to cause the data embedding module to embed thefurther data into the information signals in response to indicative dataindicating the further data is to be embedded.

[0026] According to a fifth aspect of the present invention, there isprovided an apparatus for processing information signals receivedthereby, the signals being protected by digital rights management, theapparatus having digital rights management module operable toconditionally release the information signals to a user, and a moduleoperable to embed further data in the information signals before releaseto the user dependent on indicative data indicating whether or not thefurther data is to be embedded in the information signals; wherein thefurther data, when embedded in the information signals, is perceptiblein the information signals.

[0027] Digital rights management comprises encrypting the informationsignals representing material to be sent from the server to the viewerand associating the encrypted data with rights data defining the rightsof the user. The rights data disables functions which the user is notallowed to use. For example, a user may be allowed to store and view animage but not print it, not copy it and not export it to another viewer.The rights data may be encrypted with, or separately from, theinformation signals. One or more digital signatures may be used toprotect the encrypted information signals and /or the rights data

[0028] According to a sixth aspect of the present invention, there isprovided an apparatus for sending information signals to a correspondingreceiver, the apparatus comprising a module operable to apply digitalrights management to the information signals to protect the signals fromunauthorised access thereto and to allow a recipient user conditionalaccess, according to the digital rights defined by the digital rightsmanagement, to the information signals at the corresponding receiver,and a data producer operable to produce indicative data indicatingwhether or not further data is to be embedded in the information signalsat the corresponding receiver which further data is perceptible withinformation signals, the apparatus being arranged to send to thecorresponding receiver, indicative data and data defining the form ofthe further, perceptible, data to be embedded in the informationsignals.

[0029] According to a seventh aspect of the present invention, there isprovided a method of providing an information signal to a user thereof,the method comprising the steps of;

[0030] determining the status of a potential user;

[0031] sending an information signal to a recipient apparatus of theuser together with data indicative of whether or not further data is tobe embedded in the information signal at the recipient apparatus inaccordance with the determined status of the user;

[0032] embedding the further data in the information signal at therecipient apparatus if so indicated by the indicative data, the furtherdata being perceptible in the information signal so as to degrade it;and

[0033] allowing the user access to the information signal without thefurther data embedded therein if the user complies with at least onepredetermined condition.

[0034] “Embed” as used herein is generic to superimposing further dataon the information signals, adding the further data to the informationsignals and otherwise changing the information signals so that thefurther data is in the information signals. The further data may besimply blanking applied to part of the information signals.

BREIF DESCRIPTION OF THE DRAWINGS

[0035] The above, and other objects, features and advantages of thisinvention will be apparent from the following detailed description ofillustrative embodiments which is to be read in connection with theaccompanying drawings.

[0036]FIG. 1 is a schematic diagram of a networked system for providinginformation signals to users;

[0037]FIG. 2 is a schematic diagram of an encrypted data package;

[0038]FIG. 3 is a schematic diagram of encrypted data packages which maybe used instead of that shown in FIG. 2;

[0039]FIG. 4 is a schematic diagram of a data package;

[0040]FIG. 5 is a flow diagram relating to the setting of a flag;

[0041]FIG. 6 is a flow diagram of the provision of information signalsto a customer;

[0042]FIG. 7 is another flow diagram of the provision of informationsignals to a customer;

[0043]FIG. 8A is a schematic diagram of an original image;

[0044]FIG. 8B is a schematic diagram of a bit map of a perceptiblewatermark; and

[0045]FIG. 8C is a schematic diagram of a combination of the perceptiblewatermark and the original image.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] Referring to FIG. 1, a first server 2 stores digital informationsignals representing video material, optionally with audio material, ina store 4. The store 4 may be any suitable store, including solid statememory, magnetic disc, opto-magnetic disc and tape. The video and audiomaterial is stored in compressed form or the server 2 includes acompressor 6 for compressing the material using any suitable compressiontechnique. One or more “viewers” 10 (only one shown) are linked orlinkable to the server 2 via a network 12, which may be any suitablenetwork including for example the internet. The viewers may be PersonalComputers (PCs), Personal Digital Assistants (PDAs), MP3 players, mobilephones or any other suitable programmable computing device. Each viewerincludes a decompressor 16 corresponding to the compressor 6 in theserver 2.

[0047] The server 2 applies digital rights management processing to thecompressed material. Digital rights management processors are availablefrom a variety of sources including SealedMedia, Microsoft, InterTrustTechnologies, and others. Such software, which is designed to be secureagainst unauthorised modification, allows the providers of material tosecurely distribute material over computer networks and to control theuse of the material by users. When material is to be transmitted acrossthe network 12, the digital rights management processor 8 securelypackages the material using encryption and preferably also a digitalsignature. The package includes data defining the rights of a user of aviewer to access the material. That data may be included in a file,referred to herein as the “rights file” within the secure package. Theviewer contains a corresponding processor 14 which decrypts the packagemaking the material available to the user according to the definedrights. For example, the user may be allowed only to view the material,but not store, distribute, print or otherwise process the material. Therights processor 14 in the viewer disables any functions of the viewer10 which exceed the defined rights. If a user requests the transfer ofprotected material and his or her viewer does not have the necessaryprocessor, the processor may be downloaded e.g. from server 2 via thenetwork 12 as a plug-in in known manner.

[0048] In accordance with embodiments of the present invention, theviewer 10 is provided with a processor 18 for adding a watermark to thematerial represented by the information signals after the informationsignals are decompressed. If the watermark processor 18 is not alreadyinstalled in the viewer, the lack of the watermark processor 18 isdetected by the rights management processor 14 in known manner and awatermark processor 18 is downloaded e.g. from server 2 via the network12 as a plug-in in known manner.

[0049] As shown in the example of FIG. 1, a flag is included in therights file, which flag indicates whether a perceptible watermark is tobe added to the material at the viewer 10 before it is released to theuser. The flag is set at the server 2. The flag is protected byencryption and/or by a digital signature. The encryption and /or digitalsignature applied to the flag may be the encryption and /or digitalsignature applied to the rights file or may be separate therefrom. Inthe example of FIG. 2, the information signals and rights file includingthe flag are included in one encrypted package, which optionally alsoincludes configuration data defining the configuration of the watermarkas will be discussed in more detail below. As shown in the example ofFIG. 3, the information signals, the rights file and the flag are inseparate packages. The information signals and the rights file areseparately encrypted. The flag is protected by a digital signature(SIG).

[0050] As shown in FIG. 4, the information signals, whether in theexample of FIG. 2 or 3, may include an imperceptible watermark.

[0051] Referring to FIG. 5, assuming the user of the viewer requests adownload of material from the server 2, the server 2 detects (51)whether the user is known or is a new user. If the user is known and hasa good established business relationship with the provider, the flag isset (52) to indicate that no watermark is added to the material at theviewer. If the user is a new user and/or does not have a good businessrelationship with the provider, the flag is set (53) to cause theperceptible watermark to be added at the viewer 10 as also indicated byblock 20 in FIG. 1. If the material is a still or moving image, thewatermark is visible to the user in the material and degrades thematerial.

[0052] In an alternative embodiment, the provider of the material, knowsin advance to whom he or she will send material, and knows the businessstatus of the users. The provider thus sets the flag appropriatelybefore sending the material without the need for the user to request adownload of the material.

[0053] In another embodiment of the invention, in addition to sendingthe flag, the provider sends (54) in the secure package a watermarkconfiguration file which contains data defining the form of thewatermark to be added to the material at the viewer 10. Theconfiguration data may be stored in a store 22 in the server 2. Thisenables different watermarks to be added to different material. Thewatermarks may for example identify the owners of material, who may bedifferent from the providers of the material. The watermarkconfiguration data is protected by the encryption and, if provided, thedigital signature which protects the secure package.

[0054] The system of FIG. 1 may be used in various ways, examples ofsome ways being described as follows:

[0055] a) A provider of material offers high resolution video tocustomers. The provider requires a high price to be paid for the highresolution video. The provider provides low resolution samples tocustomers free of charge so they can preview the video before buying.However the provider wishes to protect the low resolution video frommisuse by customers. Referring to FIG. 6, a customer previously unknownto the provider requests (61) a download of low resolution video fromthe server 2. The flag is set (62) at the server to add a watermark atthe viewer of the customer. The lowresolution video is downloaded (62)free of charge to the viewer. The low resolution video is stored in thestore 15 in the viewer and the watermark is added to the video at theviewer (63). If the customer then pays (64) for release of highresolution video, the high resolution video is sent (65) to the customere.g. on tape or disc by post or courier, or is securely downloaded viathe network 12.

[0056] b) Alternatively, the stored low resolution video may be adequatefor the customer's purposes and the customer pays (64) for the lowresolution video. The provider then merely resends (66) the flag thevalue of which is changed so that that the customer can retrieve (67)the video previously stored in the store 15 without the subsequentaddition of the watermark. This avoids the need to download to theviewer new video.

[0057] If a customer is known to the provider and has a good businessrelationship with the provider, the low resolution video may be sentwith the flag set to not add the watermark to the video at the viewer.

[0058] c) In another alternative, a customer may view low resolutionwatermarked video as described in a) but decide they cannot make adecision on whether to buy the video without viewing a higher resolutionsample. The customer may request that a high resolution sample be sentto them. For example they may e-mail the request to the provider. Theprovider then sends a data carrier to the customer by post or courier,the data carrier storing a high resolution sample which is visiblywatermarked. Only when the customer pays for the video and agrees tocomply with any other business conditions is an unwatermarked version ofthe video sent to the customer.

[0059] d) Referring to FIG. 7, the provider offers images for sale tocustomers. The provider offers preview images to customers for no chargeor only a small charge. The provider wishes to protect the previewimages from misuse by customers. When a customer requests (71) adownload of a preview image from the server, the provider sets (72) theflag to add a watermark to the downloaded image so that the image can beused only for preview. The image is stored (73) in the store 15 in theviewer. The customer views (73) the image with the watermark in it asthe preview image. The customer then pays (74) for the unwatermarkedimage. The provider then merely resends (75) the flag the value of whichis changed so that that the customer can retrieve (76) the imagepreviously stored in the store 15 without addition of the watermark.

[0060] One or more conditions other than payment, or additional topayment, may be applied to users who wish to access the informationsignals without embedded further data. The conditions are chosen by theprovider according to their business judgement for example.

[0061] Examples a) to d) may be applied equally to video and images.

[0062] In the examples a) to d) the digital rights management restrictsthe customers access to the video or images supplied to the viewer. Therestrictions include for example allowing the customer to view an imageor video on the viewer but not copy, print or export the image or video,or store it in another store. Those restrictions are appliedindependently of the status of the flag which determines whether awatermark is, or is not, to be embedded in the video or image at theviewer. Those restrictions are independent of business conditions suchas payment which the provider may impose. Thus even when a customer haspaid for a video or image, and the flag has been set to not embed thewatermark, the customer may only view the video or image but not copy,print, or export the video, or store it in another store.

[0063] Imperceptible watermarks may be included in the material providedby the server 2 and/or added in the viewer.

[0064] Embedding a Visible Watermark in Video or in an Image

[0065] In preferred embodiments of the invention, the watermark which isadded at the viewer is a visible watermark added to the image materialin the spatial domain. The following describes, by way of example, oneway of adding a spatial domain watermark to video or image data.

[0066] Referring to FIG. 8A, the luminance of an original image in thespatial domain is represented by pixels as is conventional. Each pixelis represented by an n bit digital number. Referring to FIG. 8B, abitmap, which is referred to hereinafter as a template, contains dataindicating which pixels of the original image are to be modified andwhich are to remain unmodified. In the example shown in FIG. 8B, pixelsm within the shaded “S” shaped area are to be modified and the otherpixels remain unmodified. “S” is only an example and any other shape canbe used. Also, a plurality of areas may be provided and they can be ofdifferent shapes. The bitmap is an example of the watermarkconfiguration data mentioned above.

[0067] In the example shown in FIG. 8C, pixels in the area of theoriginal image corresponding to the “S” shaped area of the template aremodified. The modification changes the value of the pixels. Themodification of the image degrades the image. The modification ispreferably such that it cannot be easily removed by an unauthorisedperson. The modification is such that the image, or sufficient of theimage, is recognisable so that a potential buyer can determine whetherthey wish to buy the image. However the buyer cannot remove themodification.

[0068] Examples of Modifying Pixels.

[0069] In one example all the pixel values indicated by the template areset to black thus masking-off part of the image. The user cannot removethe watermark without access to the unwatermarked image in the store 15and access is denied by the digital rights management processor 14.

[0070] The image could be a color image in which color is represented bydigital values. The image could be modified by modifying the valuesrepresenting color in the manner described above.

[0071] The preceding description assumes that the same modification isapplied to all pixels or groups of pixels. However the algorithm mayvary from pixel to pixel or from one group of pixels to another group ofpixels. For that purpose the template store may store plural-bit numbersfor each pixel or group. For example if the plural-bit number has twobits then for example 00=no change to a pixel or group, 01=modification1, 10=modification 2, and 11=modification 3. Preferably a random orderof the three modifications occurs in the template. The modifications maybe different values of luminance or chrominance applied to the pixels orgroups of pixels.

[0072] In another example, a logo is superimposed on the image.

[0073] Any one or more of the original image, the modified image and theauthorised copies thereof may have data imperceptibly embedded thereinfor copyright protection and/or to identify the image.

[0074] Whilst the invention has been illustrated by reference to videoand image signals, it may be applied to audio signals or to data.

[0075] Although illustrative embodiments of the invention have beendescribed in detail herein with reference to the accompanying drawings,it is to be understood that the invention is not limited to thoseprecise embodiments, and that various changes and modifications can beeffected therein by one skilled in the art without departing from thescope and spirit of the invention as defined by the appended claims.

We claim:
 1. A method comprising sending to a recipient apparatusinformation signals and data indicative of whether or not further datais to be embedded in the information signals, and embedding the furtherdata in the information signals at the recipient apparatus in dependenceupon the indicative data; wherein the said further data, when embeddedin the information signals is perceptible, degrading the informationsignals.
 2. A method according to claim 1, wherein the indicative datais sent together with the information signals.
 3. A method according toclaim 1, wherein the indicative data is sent separately from theinformation signals.
 4. A method according to claim 1, wherein datadefining the form of the further data is sent with the informationsignals.
 5. A method according to claim 4, wherein the indicative datais protected against modification.
 6. A method according to claim 4,wherein the indicative data is associated with a digital signaturedependent on the indicative data.
 7. A method according to claim 4,wherein the indicative data is encrypted.
 8. A method according to claim4, wherein the information signals are encrypted.
 9. A method accordingto claim 4, comprising determining whether the user of the recipientapparatus complies with at least one predetermined rule governing accessto the information signals and setting the indicative data to allow theuser access to the information signals without the embedded further dataif the user complies with the at least one predetermined condition. 10.A method according to claim 1 , wherein a user of the recipientapparatus is allowed access to the information signals without theembedded further data if the user has paid for the access.
 11. A methodaccording to claim 1, comprising; sending to the recipient apparatusinformation signals and indicative data indicating that the further datais to be embedded in the information signals at the recipient apparatus,storing the information signals without the further data embedded thereat the recipient apparatus, embedding the further data in theinformation signals and making the information signals with the furtherdata embedded therein available to a user of the recipient apparatus,resending the indicative data, indicating that the further data is notto be embedded in the information signals at the recipient apparatus,and making the stored information signals available to the user withoutthe further data embedded therein.
 12. A method according to claim 11,wherein the indicative data is resent, indicating that further data isnot to be embedded in the information signals, in response to the usercomplying with at least one predetermined condition.
 13. A methodaccording to claim 12, wherein the said condition is payment by the userfor access to the information signals without the embedded further data.14. A method according to any preceding claim, comprising the furtherstep of embedding imperceptible data in the information signals.
 15. Amethod according to claim 1, comprising compression encoding theinformation signals and sending the compression encoded signals to therecipient apparatus, decompressing the information signals at therecipient apparatus and embedding the further data in the decompressedinformation signals in dependence upon the indicative data.
 16. A methodaccording to claim 1, wherein the information signals are video signals.17. A method according to claim 17, wherein the further data is embeddedin every frame of a video signal.
 18. A method according to claim 1,wherein the information signals represent still images.
 19. A methodaccording to claim 1 , wherein the information signals are audiosignals.
 20. A method according to claim 1 , wherein the informationsignals represent audio and video.
 21. A method according to claim 1 ,wherein the information signals are data signals.
 22. A method accordingto claim 1, comprising the step of defining digital rights which controlthe use of the information signals at the recipient apparatus.
 23. Acomputer program product arranged to carry out the method of claim 1when run on a suitable computer system.
 24. A data providing mediumarranged to provide the computer program product of claim
 23. 25. Amedium according to claim 24, which is a transmission medium.
 26. Amedium according to claim 24, which is a data storage medium.
 27. Asystem for providing information signals, the system comprising one ormore servers and one or more clients linked to the server(s) by a datatransmission network, the server(s) being arranged to: a) apply digitalrights management to the information signals to protect the informationsignals against unauthorised access thereto and to allow access theretoat the client(s) according to the digital rights defined by the digitalrights management, a) provide to the client(s) indicative dataindicating whether further data is to be embedded in the informationsignals at the client(s), and the client(s) being arranged to: c)dependent on the indicative signal, embed the further data in theinformation signals before providing the information signals to theuser(s), and d) allow access to the information signals according to thedigital rights. wherein the further data, when embedded in theinformation signals, is perceptible, degrading the information signals.28. A system according to claim 27, wherein the or each client includesa store arranged to store the information signals without the furtherdata embedded therein.
 29. A system according to claim 27 whereinimperceptible data is embedded in the information signals, in additionto the said further data
 30. A system according to claim 27, wherein theserver(s) are arranged to provide compression encoded informationsignals to the client(s), the client(s) being arranged to decompress theinformation signals and embed the further data in the decompressedinformation signals in dependence upon the indicative data.
 31. A systemaccording to claim 27, wherein the information signals are videosignals.
 32. A system according to claim 27, wherein the informationsignals represent still images.
 33. A system according to claim 27,wherein the information signals are audio signals.
 34. A systemaccording to claim 27, wherein the information signals represent audioand video.
 35. A system according to claim 27, wherein the informationsignals are data signals.
 36. A system according to claim 31, whereinthe client(s) are arranged to embed the further data in every frame of avideo signal.
 37. A computer program product comprising a digital rightsmanagement module together with a module for embedding further data intoinformation signals protected by the digital rights management module,which further data is perceptible in the information signals and amodule for causing the data embedding module to embed the further datainto the information signals in response to indicative data indicatingthe further data is to be embedded.
 38. A product according to claim 37,wherein the embedding module is operable to create data to be embeddedin response to data configuration information.
 39. A product accordingto claim 37, further comprising a module for decompressing compressedinformation signals before the embedding module embeds the further datatherein.
 40. Apparatus for processing information signals receivedthereby, the signals being protected by digital rights managementtechniques, the apparatus having digital rights management moduleoperable to conditionally release the information signals to a user, andan embedder operable to embed further data in the information signalsbefore release to the user dependent on indicative data indicatingwhether or not the further data is to be embedded in the informationsignals; wherein the embedder is arranged to embed further data which isperceptible to the user in the information signals.
 41. Apparatusaccording to claim 40 further comprising a decompressor operable todecompress compressed information signals before the embedder embeds thefurther data therein.
 42. Apparatus according to claim 40, furtherindicating a store arranged to store the information signals without thefurther data embedded therein.
 43. Apparatus according to claim 40,wherein the embedder is arranged to additionally embed data which isimperceptible to the user in the information signals.
 44. Apparatusaccording to claim 40, wherein the embedder is arranged to receive theindicative data from the digital rights management means.
 45. Apparatusaccording to any one of claim 40, wherein the embedder is operable tocreate data to be embedded in response to data configurationinformation.
 46. Apparatus according to claim 45, wherein the embedderis arranged to receive the data configuration information from thedigital rights management means.
 47. Apparatus according to claim 40,for processing video signals wherein the embedder is operable to embedthe further data in every frame of a video signal.
 48. Apparatus forsending information signals to a corresponding receiver, the apparatuscomprising a module operable to apply digital rights managementtechniques to the information signals to protect the signals fromunauthorised access thereto and to allow a recipient user conditionalaccess to the information signals at the corresponding receiver, and adata producer operable to produce indicative data indicating whether ornot further, perceptible, data is to be embedded in the informationsignals at the corresponding receiver, the apparatus being arranged tosend to the corresponding receiver, the indicative data and datadefining the configuration of the further perceptible data to beembedded in the information signals.
 49. Apparatus according to claim48, wherein the apparatus is arranged to send the indicative data to thereceiver with the information signals, the indicative data beingprotected from unauthorised access thereto.
 50. Apparatus according toclaim 48, wherein the apparatus is arranged to send the indicative datato the receiver separately from the information signals, the indicativedata being protected from unauthorised access thereto.
 51. Apparatusaccording to claim 48, wherein the apparatus is arranged to send theconfiguration data to the receiver with the information signals, theconfiguration data being protected from unauthorised access thereto. 52Apparatus according to claim 51, wherein the apparatus is arranged tosend the configuration data to the receiver separately from theinformation signals, the configuration data being protected fromunauthorised access thereto.
 53. Apparatus according to claim 48 furthercomprising a module for compressing the information signals.
 54. Asignal generated by the apparatus of claim
 48. 55. A method of providingan information signal to a user thereof, the method comprising the stepsof; determining the status of a potential user; sending an informationsignal to a recipient apparatus of the user together with dataindicative of whether or not further data is to be embedded in theinformation signal at the recipient apparatus in accordance with thedetermined status of the user; embedding the further data in theinformation signal at the recipient apparatus if so indicated by theindicative data, the further data being perceptible in the informationsignal so as to degrade it; and allowing the user access to theinformation signal without the further data embedded therein if the userhas complied with at least one predetermined condition.
 56. A methodaccording to claim 55, wherein the predetermined condition is payment bythe user for access to the information signal.
 57. A method according toclaim 55, wherein the information signal sent to the user together withthe indicative data is a relatively low quality representation of thematerial for preview by the user.
 58. A method according to claim 57,wherein the user is allowed access to a relatively high qualityrepresentation of the material provided the user complies with the saidat least one condition.